The present invention relates to Data Acquisition and, more particularly, to Analog to Digital Converter (ADC).
Analog-to-digital conversion (ADC) refers to the transformation of real world physical data—which is analog in nature, namely continuous and of infinite resolution—into digital, or binary format where the size of each variable is expressed as a binary word of a prescribed length. The need for this transformation comes from the fact that any further processing of said data is commonly done digitally. The analog-to-digital transformation generally takes two stages. In the first stage the physical data is measured by an appropriate sensor that commonly translates it into a certain voltage through a given scale factor. At this stage the data is within the level of the voltage, therefore is still in the analog form. The second stage is the actual transformation of the sensor's output voltage into a digital word. This is independently done by the analog-to-digital-converter.
For example, in digital cameras, the scenery light is commonly focused by lenses on a plane inside the camera, where it is being translated into a matrix of voltages by a matrix of photo-detectors that comprises the image sensor and is appropriately placed in the camera's focal plane. The output voltages of said image sensor matrix cells or “pixels” are then sequentially sampled and inputted into the ADC that transforms the data into a matrix of digital words, that are then ready to undergo further digital image processing. In digital video cameras, as in other real-time on-line applications (e.g., flight control) the most important merits of performance of ADC are speed of conversion, stability, and accuracy—which is the ADC signal to noise ratio. In on-line real-time applications the ADC process is commonly done in hardware (HW).
HW ADC devices are therefore the subject of a quite intensive development for over quarter century now. Most of the existing ADC devices however consist of mixtures of analog and intensive, sometimes iterative, digital computations. This mixed technology approach results in rather expensive devices with inherent speed and accuracy limits, required input sample-hold with cumbersome input-synchronization, and with possible tendency to instability. Another disadvantage of mixed technology ADC is great hazard of digital to analog cross-talk that causes electronic noise which further jeopardizes the conversion accuracy.
There is thus a widely recognized need for, and it would be highly advantageous to have, an only-analog ADC that does not need input sample-hold and synchronization, whose signal flow is strictly unidirectional, with no digital-to-analog cross-talk, and thereby with no room for configuration-induced instability, or configuration-induced speed and accuracy limitations.